Sizing of paper



Patented Apr. 16, 1940 UNITED STATES PATENT ori ce Charles R. Outtenon, Syracuse, n. Y. )No :61!!! 1B, 1936,

80mins.

.This invention relates to the manufacture of paper and more particularly to that portion of the process which is concerned with the incorporation of sizing materials in paper pulp- The ultimate objects of the. invention are to cause more complete adsorption or retention of the size from the size solution or emulsion by fibers treated therewith; to speed. up the sizing process; to reduce the quantity ofsizing materials required; to cause the size to be deposited uniformly in the fibers in extremely fine particles; to avoid excessive foaming of the stock during formation into paper and to avoid the deposition of resinous matter upon the various parts of'the paper machine which come into contact therewith.

Many attempts have heretofore been made to cause the fibers to take'up a larger proportion of the sizing materialand to accomplish these other objects, but as far as I am aware no one prior to myself has devised a commercially practical means or process of attaining them.

I have discovered that the above mentioned objects may be obtained by the simple expedient of inducing a substantially complete and rapid coagulation of the rosin size or other size by alum, ,into discrete particles of a complex rosin-alum precipitate. Through this procedure, adsorption or deposition of almost the whole quantity of the sizing material upon the fiber is accomplished.

Contrary to general belief, no commercial grade of alum when employed by itself in the precipitation of rosin size causes a quantitative coagulation of all the rosin. It is true, however, that alum causes quantitative coagulation under proper conditions in pure aqueous solutions or emulsions of rosin of concentrations equivalent to those found in practice, but in the presence of fiber, which itself possesses colloidal properties, and under practical paper making conditions complete coagulation of rosin is not obtained, apparently because of a colloidal protection of the rosin. This colloidal protection is particularly evident where protective colloids are added for the specific purpose of stabilizin :the rosin against premature precipitation, or of controlling the fineness of the particles of the precipitated rosin.

In accordance witl'i the principal embodiment of the present invention, the complete, or substantially complete,- coagulation of the rosin size is induced or caused to take place by the introduction of small quantities of formaldehyde and of phenol, which materials may be added directly to the beater or may be incorporated into any of the as raw materials entering into the paper such as (CL 9H1) the alum is added, or may be added at any time during the action of the alum upon the rosin size. Protective colloids, such as glue, starch and the like, are preferably employed with the size and the alum, but such are not necessary for the successful action of thephenol and formaldehyde. The quantity of phenol and formaldehyde required in the present process is quite small, that is, less than 1% each, which amounts are insumcient to coat the fibers to any appreciable extent. Ordinarily, a quantity of phenol equal to 0.03% and a quantity of formaldehyde equal to 0.1% is suflicient, both percentages being based upon the weight of the rosin or other size employed. The exact percentages depend upon the circumstances or conditions under which the same are employed and also the desired rate of coagulation.

I have discovered that effective use of the above reagents in conjunction with protective colloids is dependent upon the absence of free or uncombined alkali in a quantity which destroys or interferes with the protective action of the colloid at the temperatures employed. Since many colloids are sensitive to free alkali, it is essential to the success of the present process when such colloids are included that such alkali be removed, or that lower temperatures be used. Its removal may be accomplished in any number .of ways, but it is preferred to effect .the same by heating the size'i'or a suflicient time to atemperature, that of boiling being preferred, which. causes complete reaction of the free alkali, the

absence of which may be determined by test.

Therefore vwhere colloids which are sensitive to alkali are employed, the" present invention includes the step of initially removing the free alkali before the colloid is added to the size. Where alkali stable colloids are employed, the presence of alkali is not objectionable and an initial treatment is not required.

The preferred and most practical procedure involves thesteps in the order named, which comprise removing the free alkali from the rosin size by boiling the same for a period suflicient to complete the reaction of the free alkali with the slight excess of uncombined or free rosin, introducing a protective colloid of the nature herein described and then adding. the phenol and the formaldehyde to the combination size.

The action of the phenol and the formaldehyde is not clearly understood, but it is believed that they combine with or act upon either the rosin or the colloid, or both, thereby causing the rosin and the colloid to become more senstitive to the precipitating action of the alum. They may be introduced into the heater or into the stock as such or in the form of a partial condensation product, or as a combination product with rosin, with the colloid, or with the alum.

In accordance with a second embodiment of the present invention, more complete and rapid coagulation of the size is obtained by simply adding a mere trace of a colloidal material, for example, animal glue, casein, or other harmless colloids. Roughly considered, the .quantity is about oneflftieth of that required for any substantial protective colloidal effect. One-hundredth of a pound of the colloid to each ton of paper is more than enough under most circumstances. Half that amount is generally enough.

In accordance with a third embodiment of the present invention, the coagulation of the rosin size from the rosin solution or emulsion is 'accomplished by adding to the alum solution a substance which removes a small proportiori' of the sulfuric acid formed by the hydrolysis of thealuminum sulfate by reaction which forms a substantially insoluble precipitate. This precipitation leaves the solution with such properties that upon further dilution with water and further dissociation of the alum, a higher proportion of positively charged colloidal particles of basic aluminum sulfate or aluminum hydrate is obtained. Bythis procedure, mutual adsorption of the residual colloidally dispersed rosin and the basic aluminum sulfate or aluminum hydrate results. Suitable compounds for reacting with the sulfuric acid include calcium carbonate or hydrate or other equivalent alkaline earth salts. Other methods of removing the sulfuric acid are also satisfactory.

Because of more complete and rapid coagulation of the rosin size in accordance with the tion of sticky resinous matter on the parts of the paper machine which come in contact therewith.

In the appended claims. it should'be understood that where alum is specifled such term should be interpreted as including aluminum sulfate.

It should be understood further that the present invention is not limited by the speciflc'details set out in the specification, but that it should be interpreted in accordance with the scope o the claims appended hereto.

I claim:

v1. In the manufacture of paper, the method of accomplishing a more rapid and complete coagulation in paper pulp of rosin. size containing a protective colloid, upon addition of alum, which comprises incorporating with the pulp, rosin size and alum, a small amount of phenol and of-formaldehyde each constituting not more than 1% by weight of the size, the said size being free of uncombined alkali in a quantity which interferes with the action of the colloid at the temperatures accomplishing a more rapid and complete coagu lation in paper pulp of rosin size containing a protective colloid, upon addition of alum, the step which comprises effecting in the paper pulp coagulation with alum aided by the presence of phenol and formaldehyde, each of the latter two substances being present in an amount constituting less than about one percent of the rosin size by weight, said size being free of an amount of uncombined alkali which if present would'vitiate the effect of the protective colloid at the temperature employed.

4. In the sizing of paper, the steps which comprise mixing paper pulp with a dispersion of a rosin size, alum and a small amount of phenol and formaldehyde, each constituting not more than 1% by weight of the size, and causing the fiber to adsorb or take up the size coagulated by alum and said phenol-formaldehyde.

5. In the sizing of paper, the step which comprises coagulating in paper pulp an emulsion of a. rosin size freed of uncombined alkali and containing a protective colloid, by the action of alum and a small amount of phenol and .of formaldehyde, each constituting not more than 1% by weight of the size.

6. In the treatment of paper pulp with rosin size, a protective colloid and alum, the novel combination of steps comprising removing uncombined alkali from the size, adding the size and plum to the paper pulp and inducing a m'ore complete coagulation of said size than obtainable by the alum alone by adding a small amount of phenol and of formaldehyde each constituting not more than 1% by weight of the size.

"I. In the sizing of paper with a dispersion of rosin size and alum the step which comprises inducing more complete coagulation of the size than obtainable by the alum alone by-adding to the size about 0.03% phenol and about 0.1% formaldehyde both percentages being calculated upon the amount of the size employed, by weight, the coagulation of the size in paper pulp being accomplished for the most part by the addition of alum.

8. In the manufacture of paper, the method of inducing more complete than ordinary coagulation of' dispersed sizing materials obtainable by alum alone when the same is added, which comprises heating rosin size containing free rosin until substantially all free alkali has reacted with excess free rosin, incorporating a protective colloid with the rosin size and coagulating the size in paper pulp by the action of alum and under 1% each by weight of phenol and formaldehyde based on the weight of the size.

W R. OU'I'I'ERSON. 

